User blog comment:Rbaer/8th gym!/@comment-32358261-20171129054311

In my opinion, the most likely types are

Psychic or Rock. Rock shares the fighting weakness like the dark gym (this is a trend every 2 gyms). Also there is a tm for it and it’s not too crazy to think an island would have home for rock Pokémon.

Psychic is pretty likely too since it shares a bug weakness with dark. There is still a tm for it too. Also hoopa is psychic.